This invention relates to the protection of buildings from subterranean termites and is particularly concerned with physical termite barriers for incorporating into concrete slab-on-ground buildings having a masonry veneer cladding, during their construction.
Subterranean termites typically build nests just beneath the soil surface and forage, principally for cellulose containing material, for distances which can reach hundreds of meters from their nests. Termite damage to buildings, particularly residential buildings can be as many as one building in five in some parts of Australia, costing the community many tens of millions of dollars annually in the repair of the affected timber. As a result, the Australian Building Code has made it compulsory for all new buildings to incorporate suitable termite barriers. The current Building Code is laid down in Australian Standard 3660.1-1995. This standard specifies three permissible systems for protecting concrete slabs from termite penetration. The systems comprise the use of stainless steel mesh, graded stone or chemicals.
Chemical soil barriers have recently come under attack by environmentalists on the basis that their toxicities may be harmful to man. This has lead to the banning of conventional chemicals and the use of more environmentally friendly materials. Unfortunately such materials are less effective and may have no effect whatsoever after as little as twelve months from application.
Graded stone barriers must satisfy a large number of criteria to be effective. The stones must be of crushed igneous or metamorphic origin, be from a sound source, have a minimum sg of 2.52, and be graded and shaped so that the termites cannot lift them or penetrate their voids. A typical product meeting these requirements is GRANITGARD.RTM. which is a granite stone supplied by CSR Readymix, a Division of CSR Limited. The problem with such products, however, is that they cannot effectively be used on sloping ground surfaces, supply in many parts of Australia is difficult, and they are relatively expensive.
Stainless steel mesh barriers are consequently now in widespread use. These barriers are, nevertheless, not without their drawbacks. Apart from their relatively high cost which cannot be avoided, there are particular problems when it comes to their installation at the perimeter of concrete slabs having masonry veneer walls. The commonly used method comprises parging an inner edge of the mesh to the perimeter of the slab and extending the mesh out under the row of bricks which is substantially level with the slab. The parging material is an adhesive which is required to be termite resistant, form a strong bond between the mesh and the concrete, and be durable over the life expectancy of the building. In practice, however, it is difficult to form a proper seal with the parging material due to the relative movement between the bricks and the concrete slab due to different rates of drying, and expansion and contraction taking place. The integrity of the seal is therefore frequently broken and regions for termite entry are provided.